1. Field
The present invention relates generally to computer security and, more specifically, to providing time in a computing platform that is trusted by executing applications.
2. Description
Obtaining a value for time that can be trusted in a computing platform is desirable. For example, trusted time may be used in conjunction with other processing to improve the robustness of content protection mechanisms to assure that premium content is available for the digital home. It may be used in a content protection environment to assure that the computing platform owner downloads a revocation list of compromised keys on a periodic basis. It may also be used to provide a secure way to enable content to be purchased for access during a temporary time window. However, if the time value can be modified by an unscrupulous user without detection by the computing platform, then computer security and content protection systems may be compromised.
Existing solutions to providing trusted time require a battery contained in a tamper resistant hardware module that cannot be easily removed by the user (such as described in Trusted Platform Module (TPM) Main part 1 Design Principles, Specification Version 1.2, Revision 81, Nov. 23, 2004, pp. 93-98, available from the Trusted Computing Group). This may be problematic for continued operation of some computer systems as they age and the battery needs replacement. If the user can't change the battery without disrupting system operation, frustration with the system may ensue.
Therefore, a better mechanism to provide a trusted time value in a computing platform would be useful.